Fluidized bed reactor

ABSTRACT

A fluidized bed reactor featuring a self-contained prefabricated wind box structure.

United States Pater 1t 1 mc1.. L ..F27h15/00 72 lriventor Robin 0. F.Nauta 1501 Field at Search .L34/57 R, 57 Sta mlord, Conn. A; 263/21 A[21] Appl. No. 863,816 [22] Filed Oct. 6, 1969 Relerences Cited [45]Patented Aug. 10,1971 UNITED STATES PATENTS 1 Assignnorr-oliv'erlnwrpormd 2,529,366 11/1950 Bauer 263/21 A stam o dfi n2,782,019 2/1957 Turney etal..... 263/21 A 2,789,034 4/1957 -Swaine etal 34/57 A 5 FLUIDIZED BED REACTOR Primary Examiner-John J- Camby I l c19 Drawing Figs. Attorneys-Theodore M. Jablon and D. M. Mezzapelle 1521u.s.c1. .l 26am A, 34/57A ABSTRACT: A fluidized bed reactor featuring aself-contained prefabricated wind box structure. j

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FLUIDIZED' BED REACTOR This invention relates to continuously operatingfluidized bed reactors wherein a bed of solid particles is treatedorreacted with, or subjected to combustion, with a fluidizing gas suppliedunder pressure through a wind box which supports the bed in a state offluidization.

From the wind box the gases rise into areaction chamber or zonereceiving a continuous supply of the material to be treated, while thesolids and/or gaseous reaction products are continuously removed.

The behavior, appearance, and physical characteristics of the bed offluidized material are comparable to those of a body of boiling liquidthe specific gravity of which depends upon the density at which bed ismaintained by the upflowing fluidizing gas.

The spent hot gases resulting from the combustion or other chemicalreactions or other fluidizing treatment operation, along with dustparticles blown from the bed escape as stack gases from the top end ofthe reactor unit. The dust particles in the stack gases are usuallytrapped in a cyclone followed by a scrubber. The wind box gas pressuremust be high enough to overcome the sum total of flow resistancesincluding pressure differential across the constriction plate plus thedifferential needed for sustaining the fluidized condition of bed.

Examples of fluidized bed operation, applicable to this invention arefound in metallurgical operations such as the fluidizing gas, thecombustion of dewatered moist sewage sludge in a bed of hot sandfluidized by the combustion air (disclosed in U.S. Pat. to No. 3,319,586to Albertson and Budd); the heating or drying of the material as byinert hot combustion gases; or the cooling of treated hot material by afluidizing gas or by air being thus preheated for use in a subsequenttreatment or oxidizing treatment in a fluidized bed.

The invention is applicable to a type of reactor having a basicallyelongate rectangular configuration, as distinguished from thecylindrical type which has a constriction plate. The so-called tuyeresor nozzles inserted into the openings of the constriction platedistribute the fluidizing gas into the bed, while preventing backflow ofthe material downwardly through the plate during periods of interruptionof the operatron.

In the cylindrical type of reactor the material to be treated must beintroduced by way of one or a plurality of feeders spaced from oneanother along the periphery of the reactor shell. Aside from arelatively cumbersome feed apparatus leading to, and surrounding thecylindrical reactor, there is a drawback in that the material undergoingtreatment or combustion may not be evenly distributed across the area ofthe bed, so that substantial portions'of the fluidizing gas or-air andof the bed area, particularly the central portion thereof, are lost.

Another problem of the cylindrical-type reactor of large diameter is dueto wind box gas pressure exerted upon the underside of the constrictionplate, especially where the constriction plate is of a compositerefractory block construction supported by the surrounding walls of thereactor.

While the rectangular elongate-type reactor may avoid uneven orinadequate feed distribution in the bed, for instance where a materialin state of fluidization is caused to move over the elongateconstriction plate from inlet end to outlet end of the reactor, there isnevertheless inherent in this type of rectangular reactor the problem ofcontaining the required wind box pressure against the planar walls ofthe wind box chamber and against the constriction plate itself, eventhough the width of the constriction plate may be small relative to itslength.

In view of the above-stated problems, it is one of the objects of thisinvention to provide a reactor with a wind box that is highly pressureresistant in its own right, while avoiding the problems of theconventional constriction plate.

Another object is to provide a reactor having a simplified feedarrangement whereby an effective and substantially uniform and rapiddistribution is attainable of the feed material over the area of thefluidized bed.'

Another object is to provide a compact elongate system or assembly ofreactor units, capable of being extended bythe lengthwise addition ofsuch units.

Still another object is to provide a wind box structure that is freefrom the above-stated drawbacks of the conventional, and independent ofthe wall support.

In order to attain the foregoing objectives, this invention provides areactor unit with a wind box in the form of a separately prefabricatedwind box structure located in the lower portion of the reactor shell,and defining a treatmentor combustion chamber in the complementary upperportion of the shell. Thiswind b ox structure is connected to a supplyof fluidizing gas under pressure, and has delivery means or tuyeres fordistributing the gas upwardly into a bed of material to be fluidized inthe treatment-or combustion chamber.

According to one feature, an elongate rectangular reactor unit havingsidewall, end walls, a bottom, and a roof is provided with a wind boxstructure of cylindrical or tubular shape, which may be horizontallycoextensive with the elongate shape of the reactor. This feature mayalso be embodied in a wind box structure comprising a plurality ofparallel elongate intercommunicating chambers.

Another feature of the invention lies in the provision of a plurality offeeders or self-contained feeding devices horizontally spaced from oneanother along the length of the reactor, and so arranged that thematerial to be burned in the fluidized bed, for instance dewateredsewage sludge or the like, is distributed effectively by the feedersover respective transverse sections or zones of the elongate fluidizedbed.

For the purpose of waste disposal, a plurality of rectangular reactorunits may be connected lengthwise to one another, providing-a compositereactor system with feeders located all along one side of the system,each component unit being equipped with its own supply of fluidizingair, and its own exit for the combustion gases. Thus, the capacity of anexisting reactor of this type may be increased by the additionlengthwise of component units.

Other features and advantages will hereinafter appear.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is (embodiments are) illustrative and not restrictive. Thescope of the invention is defined by the appended claims rather than bythe description preceding them, and all embodiments which fall withinthe meaning and range of equivalency of the claims are thereforeintended to be embraced by those claims.

FIG. 1 is a longitudinal sectional view of a reactor, exemplifying theprefabricated wind box in the form of a tubular chamber, and suited forthe combustion of waste matter with laterally arranged feed devicesleading into the combustion chamber.

FIG. 2 is a plan view of the reactor taken on line 22 of FIG. 1.

FIG. 3 is a cross-sectional view taken on line 3-3 of FIG. 1.

FIG. 4 is a fragmentary cross-sectional view of the reactor, showing adifferent form of the tubular concept of the wind box structure.

FIG. 4 is a plan view taken on line 4"-4" of FIG. 4.

FIG. 5 is a fragmentary view similar to FIG. 4 showing a multiplicity oftubular chambers.

FIG. 6 is a fragmentary cross-sectional view similar to FIG. 5, with thetubular chambers forming a planar top face supporting the fluidized bed.

FIG. 7 is a similar fragmentary cross-sectional view, of a wind boxstructure in the form of a shallow rectangular chamber with stay boltsor the like .interconnecting the top and bottom plates of the chamber.

FIG. 8 is a plan view taken on line 8-8 of FIG. 7.

FIG. 9 is a side view of a lengthwise assembly of rectangular reactorunits embodying the invention, suited for the combustion of waste matterwith laterally arranged feed devices.

FIG. 10 is a plan view taken on line 10-10 of FIG. 9.

FIG. 11 is a longitudinal sectional view of the reactor, generallysimilar to FIG. 1, but suited for the treatment of materials with feedinlet at one end, and discharge for the treated material at the oppositeend of the reactor.

FIG. 12 is a part-sectional plan view of the reactor, taken on line12-12 in FIG.'11.

FIG. 13 is a longitudinal sectional view of the reactor similar to FIG.1 with laterally arranged feed devices, additionally equipped with anair preheater tube system located in the combustion chamber.

FIG. 14 is a part-sectional view of the reactor, taken on line 14-14 ofFIG. 13.

FIG. 15 is a skeleton view in perspective of the air preheater tubesystem of FIGS. 13 and 14.

FIG. 16 is a plan view of a wind box structure having individual windbox chambers each having an individually controllable supply offluidizing air.

FIG. 17 is a cross-sectional view taken on line 17-17 in FIG. 16,illustrating the effect of the individual control.

FIG. 18 is a cross-sectional view similar to FIG. 17, showing amodification.

A longitudinal rectangular reactor as exemplified in the embodiment ofFIGS. 1 to 3, is applicable to the combustion of waste material forinstance of thickened sewage sludge, where the waste is fed into afluidized bed of hot sand maintained at combustion temperatures.

In this embodiment, the reactor comprises an elongate housing 10 havinga bottom 11, a low end wall 12, a high end wall 13, a roof 13" slopingdown from the high end to the low end, and a pair of sidewalls l4 and15. The housing is indicated as comprising a steel shell 10'' providedwith a refractory lining 10'. The housing has an auxiliary-or startingburner 16 at the low end, and a dust-separating cyclone 17 at the highend for the combustion gases. The sloping roof ac-. commodates the flowof the combustion gases that increase in volume from the low end to thehigh end of the reactor, where an exit pipe 18 for the gases leads intothe cyclone from which a pipe or stack 19 delivers the dust-free gasesinto the atmosphere. lntercepted dust or ash particles are dischargedthrough a cellular wheel 20 or other suitable discharge devices.

The housing contains a wind box 20 which according to this invention isa prefabricated self-contained structure occupyingthe lower portion ofthe housing. The space above this wind. box represents the treatment-orcombustion chamber 21 containing the fluidized bed 22. In thisembodiment the wind box is in the form of tubular chamber coextensivewith longitudinal extent of the housing, and designed to readily containthe wind box pressure of the fluidizing gas. In this way, the walls ofthe housing itself are subjected only to a much lower pressure which maybe a fraction of the required wind box operating pressure.

The fluidizing gas under pressure is supplied by a blower 23 connectedthrough pipe 23" to the wind box preferably at the low end of thehousing. Air nozzles or so called tuyeres 24 mounted on the wind boxchamber. distribute the combustion air into a bed of sand keeping thesame fluidized. A plurality or row of screw feeders 24" or othersuitable feeding devices for the waste material are mounted in one thesidewalls of the housing, horizontally spaced from one another, so thateach feeder supplies waste material to a transverse area or section S ofthe fluidized bed. Hence, with the length of the rectangular reactorshown to be substantially greater than its width, the arrangement issuch that each feeder will supply the associated section S of the bed insuch a manner as to maintain substantially uniform combustion across thearea of the bed.

Combustion of the waste material in the fluidized sand may beself-sustained where the moisture of the waste material or sewage sludgehas been sufficiently reduced. But if need be, the combustion may beaided by the addition of supplemental fuel supplied for instance toburner 16, or otherwise. Also, preheating of the combustion air may beemployed for maintaining required combustion temperatures.

An air preheating tube system 25 for heat exchange with the combustiongases is shown in FIGS. 11, 12 and 13, located within the combustionchamber itself. While the reactor is shown to be substantially the sameas the one above described (FIGS. 1 to 3), the tube system 25 in apreferred form dorm prises a horizontal air inlet header 26 at the highend of the housing, a hot air discharge header 27 at the low end of thehousing, and a plurality or bundle of heat exchange tube elements 28interconnecting the headers 26 and 27. The inlet header has a supplyconnection 29 for compressed air, extending through the high wall to ablower not shown, while the discharge header has one or more connections29 for delivery of preheated air into the adjacent end of the wind boxchamber. Two such delivery connections are shown, providing between themthe space for accommodating the auxiliary burner 16. The tube elementsin this embodiment are shown to be identical and parallel to oneanother, and generally shaped to follow the inner contour of thehousing. Thus, these tube elements comprise a vertical end portion 28leading from header 26, a sloping portion 28 leading to header 27, andan intermediate bend portion 28.

The self-contained or prefabricated wind box of this invention mayassume a variety of structural forms such as are illustrated in FIGS. 4,4", 5, 6, 7, and 8. According to the embodiments in FIGS. 4, 4, and 5, acomposite wind box structure comprises two or more tubular chambers 29side by side and of smaller diameter than the one in FIG. 3. An outsidehorizontal supply header 29 for compressed air has branch connections 30with the respective adjacent ends of the chambers or tubes 29. Each ofthese tubes may have one or more rows of air discharge nozzles ortuyeres 31 spaced from one another along the length of the tubes. Theremay be on each tube or chamber a central row of tuyeres 31 flanked byrows supplemental orifices 32 each of which has an air distributionshield 33 to prevent back seepage of particles of the bed materialthrough the orifices. It will be understood that the tuyeres 31 may beof a suitable well-known type constructed to prevent back seepage ofparticles therethrough in case of shutdown of the reactor.

In the embodiment of FIG. 6, a composite wind box structure comprises aplurality of individual elongate chambers 34 side by side as those inFIG. 5, but of rectangular cross-sectional configuration, and thusproviding a planar top face F-l to support the fluidized bed. Nozzles ortuyeres 35 provided in any suitable disposition are thus all located ina common horizontal plane.

In the embodiment of FIGS. 7 and 8 a single wind box structure 36 isofactual box construction presenting a planar top face F-2 supporting afluidized bed. This wind box therefore comprises a bottom plate 36 a topplate 36, interconnected by vertical walls 36, with nozzles or tuyeres37 mounted in the top plate and thus located in a common horizontalplane. Vertical stay bolts 38 surrounded by tubular spacers 39 rigidlyinterconnect the top and bottom plates, thus rendering them highlyresistant to the fluidizing gas pressure.

The underlying concept of this invention, that is the selfcontained orprefabricated wind box structure, may also be embodied in the circularor cylindrical type of reactor, with the wind box structure thanassuming a cylindrical or pill box" shape.

According to FIGS. 9 and 10, a number of combustion-type reactors,operating in the manner of the ones above described, may be connectedlengthwise to one another, but with a common fluidized bed extendingfrom end to end of this assembly. Accordingly, a composite housingstructure of the length L-l comprises modular housing sections of thelength L-2 each of which in turn is equipped with its own self-containedor prefabricated wind box system 40 and compressed fluidizing air supply41, feed devices 42 for the waste matter or sewage sludge to bedestroyed by thermal oxidation, and a cyclone 43 for the combustiongases, provided with a stack 43".

The reactor shown in FIGS. 14 and 15 although generally similar to theone shown in FIGS. 1 to 3, illustrates the use of this invention influidized bed treatment operations other than the waste combustionprocess presented in the .preceding embodiments. Such other treatmentoperations as previously stated, may comprise calcining, roasting,drying-, or cooling operations where the material being treated orchemically altered constitutes the material of the fluidized bed itself.Accordingly, in this embodiment, a supply connection 47 allows thematerial to be treated to enter the reactor and the fluidized bed 45 atone end, preferably the low end of the reactor. A cyclone 46 may be usedfor separating the dust from the gases resulting from the operation. Theopposite or high end of the reactor has a discharge connection 44 forthe treated material which is thus caused to flow or travel from theinlet end to the outlet end of the reactor, while undergoing therequired treatment or chemical conversion. An auxiliary burner 48 ishere shown to be disposed in the roof of the reactor housing at theloweror feed end thereof.

The embodiment in FIGS. 16, 17, and 18 according to the inventionprovides individual controls for the supply of fluidizing air to aplurality of wind box chamber constituting the wind box structure.Accordingly, in the example of FIGS. 16 and 17 an elongate rectangularreactor casing 48 contains a wind box structure consisting of threetubular horizontal parallel wind box chambers 49, 50, and 51, eachhaving air discharge nozzles or tuyeres 52 such as previously referred,and an example of which is found in U.S. Pat. No. 2,841,476 to Dalton.An outside supply header 53 for the fluidizing air has branch connection54, 55, and 56 with the adjacent ends of respective tubular wind boxchambers. The branch connections in turn have control valves 57, 58, and59 respectively. The valves may be operated in sucha manner thatfluidizing air is delivered relatively more intensely from the lateraltubular chambers 49 and 51 than from the central chamber 50, asindicated by flow arrows A-l, A-2, and A-3 respectively, in order thatas a net result the fluidizing effect should be distributed more evenlyacross the area of the fluidizing bed. The modification in FIG. 18illustrates a similarly controlled fluidizing effect with a large numberof tubular wind box chambers.

lt will be understood that this feature of selectively controlling therate of supply of the fluidizing gas to the individual wind box chambersof a composite wind box structure is applicable to any of the foregoingembodiments wherein the wind box chambers have an external supply headerand branch connections from the header to the adjacent ends of the windbox chambers. It will also be understood that the term horizontaltubular containers designating the individual wind box chambers mayinclude those of circular-as will those of rectangular cross section.

lclaim:

1. A fluidized bed reactor which comprises a reactor shell, aprefabricated wind box structure built for containing wind box gaspressure, located in the bottom portion of the reactor shell, anddefining a combustion chamber in the complementary upper portion of saidshell, said wind box structure having delivery means for distributing afluidizing gas into a bed of material to be fluidized,

conduit means connected to the wind box structure for supplyingfluidizing air under pressure,

feed means for supplying material for combustion into the combustionchamber,

and exit means for the combustion gases.

2. The reactor according to claim 1, wherein said gas delivery means ofthe wind box structure comprises nonsifting tuyere units.

3. A fluidized bed reactor which comprises a reactor shell ofrectangular elongate configuration, having a bottom, longitudinalsidewalls, end walls, and a roof,

a prefabricated wind box structure built for containing wind box gaspressure, located in the bottom portion of the reactor shell andsubstantially conforming to the inner contour of said bottom portion,and thus defining a combustion chamber in the complementary upperportion of said shell, said wind box structure having delivery means fordistributing a fluidizing gas into-a bed of material to be fluidized;conduit means connected to the wind box structure for supplyingfluidizing air under pressure; feed means for supplying material forcombustion into combustion chamber,

and exit means for the combustion gases.

4. The reactor according to claim 3, wherein said wind box structurecomprises a plurality of horizontal tubular containers in side-bysidearrangement, an external supply header for the fluidizing gas withbranch connections leading from the supply header to the adjacent endsof respective containers.

5. The reactor according to claim 3, wherein each of said branchconnection have valve devices operable for individually controlling therate of supply of the fluidizing gas to the respective containers.

6. The reactor according to claim 3, wherein a plurality of feed devicesare provided horizontally spaced from one another.

7. The reactor according to claim 3, wherein a plurality of feed devicesare provided horizontally spaced from one another along one side of thereactor.

8. The reactor according to claim 3, wherein said wind box structurecomprises at least one horizontal tubular container coextensive with thelongitudinal extent of the reactor.

9. The reactor according to claim 3, wherein said wind box structurecomprises a plurality of horizontal containers in a side-by-sidearrangement, and communicating with one another.

10. The reactor according to claim 3, wherein said reactor shellcomprises a sequence of tunnel-shaped sections connected endwise to oneanother so as to constitute a composite reactor system, with a fluidizedbed adapted-to extend from end to end of the system, each said sectionhaving at least one feed device, a stack for the combustion gases, and aself-com tained wind box structure provided with individuallycontrollable air pressure supply devices.

11. The reactor according to claim 3, wherein said gas delivery means ofthe wind box structure comprises nonsifting tuyere units.

12. A fluidized bed reactor which comprises a reactor shell ofrectangular elongate configuration, having a bottom, longitudinalsidewalls, end walls, and a roof,

a prefabricated wind box structure built for containing wind box gaspressure, located in the bottom portion of the reactor shell andsubstantially conforming to the inner contour of saidbottom portion, andthus defining a combustion chamber in the complementary upper portion ofsaid shell, said wind box structure having delivery means fordistributing a fluidizing gas into a bed of material to be fluidized;

conduit means connected to the wind box structure for supplyingfluidizing air under pressure;

feed means for supplying material for combustion into the combustionchamber,

exit means for the combustion gases, an air preheater tube systemlocated within the combustion chamber, and comprising a transverse inletheader located at one end of said chamber and adjacent one end of saidwind box structure, a transverse outlet header located at the other endof said wind box structure, a plurality of tubes arranged side by sideand substantially parallel to one another, intercon necting said inletheader and said outlet header, a cool air supply connection for saidinlet header, and a connection between said outlet header and. theadjacent end of said wind box structure, for passing preheated air intosaid wind-box structure.

13. The reactor according to claim 12, wherein said exit means for thecombustion gases are located adjacent to said inlet header.

14. The reactor according to claim 12, wherein a plurality of feeddevices are provided horizontally spaced from one another.

the

15. The reactor according to claim 12, wherein a plurality of feeddevices are provided horizontally spaced from one another along one sideof the reactor.

16. The reactor according to claim 12, wherein said wind box structurecomprises at least one tubular container coextensive with thelongitudinal extend of the reactor.

17. The reactor according to claim 12, wherein said wind box structurecomprises a plurality of horizontal ducts in sideby-side arrangement,and communicating with one another.

18. The reactor according to claim 12, wherein said wind box structurecomprises a plurality of horizontal ducts in sideby-side arrangement,and an external supply header for the fluidizing gas with branchconnections leading from the supply header to the adjacent ends ofrespective ducts.

19. The reactor according to claim 12, wherein said wind box structurecomprises a plurality of horizontal ducts in sideby-side arrangement, anexternal supply header for the fluidizing gas with branch connectionsleading from the supply header to the adjacent ends of respective ducts,and said branch connections are provided with valve devices operable forindividually controlling the rate of supply of the fluidizing gas to therespective ducts.

20. The reactor according to claim 12, wherein said wind box structureis in the form of a box having a flat top plate and a bottom plate, andis provided with internal stiffening means connecting the top plate withthe bottom plate.

21. The reactor according to claim 12, wherein said stiffening meanscomprise bolts surrounded by spacer tubes.

22. The reactor according to claim 12, wherein said wind box structurecomprises a plurality of ducts of rectangular cross-sectionalconfiguration arranged side by side, and having their top faces extendin a common plane.

23. A fluidized bed reactor which comprises a reactor shell ofrectangular elongate configuration, having a bottom, longitudinalsidewalls, end walls, and a roof, said shell being functionally dividedinto a wind box chamber and a combustion chamber above the wind boxchamber, so that a fluidizing gas supplied under pressure to the windbox chamber rising into the reaction chamber will sustain a body ofparticulate material in a fluidized state,

conduit means connected to said wind box chamber to supply combustionair under pressure,

exit means for the combustious gases from the combustion chamber,

and a plurality of feed devices horizontally spaced from one anotheralong the length of the reactor.

24. A fluidized bed reactor which comprises a reactor shell, aprefabricated wind box structure built for containing wind box gaspressure, located in the bottom portion of the reactor shell, anddefining a treatment chamber in the complementary upper portion of saidshell, said wind box structure having delivery means for distributing afluidizing gas into a bed of material to be fluidized,

conduit means connected to the wind box structure for supplyingfluidizing gas into the wind box under pressure;

feed means for supplying material to be subjected to fluidizationtreatment in said chamber,

discharge means for delivering treated material from said chamber,

and exit means for the spent fluidizing gases.

25. The reactor according to claim 24, wherein said gas delivery meansof the wind box structure comprise nonsifting tuyere units.

26. A fluidized bed reactor which comprises a reactor shell ofrectangular elongate configuration, having a bottom, longitudinalsidewalls, end walls, and a roof;

a prefabricated wind box structure built for containing wind box gaspressure, located in the bottom portion of the reactor shell, and thusdefining a treatment chamber in the complementary upper portion of saidshell, said wind box structure conforming to said elongateconfiguration, and having delivery means for distributing a fluidizinggas into a bed of material to be fluidized;

conduit means connected to the wind box structure for supplyingfluidizingfas into the wind box under ressure; feed means locate at oneend of the reactor, or supplying material to be subjected tofluidization treatment in said chamber,

discharge means for delivering treated material from said chamber at theother end of the reactor,

and exit means for the spent fluidizing gases.

27. The reactor according to claim 26, wherein said gas delivery meansof the wind box structure comprise nonsifting tuyere units.

28. The reactor according to claim 26, wherein said wind box structurecomprises at least one horizontal tubular container coextensive with thelongitudinal extent of the reactor.

29. The reactor according to claim 26, wherein said wind box structurecomprises a plurality of horizontal containers in side-by-sidearrangement, and communicating with one another.

30. The reactor according to claim 26, wherein said wind box structurecomprises a plurality of horizontal tubular containers in side-by-sidearrangement, an external supply header for the fluidizing gas withbranch connections leading from the supply header to the adjacent endsof respective tubular containers.

31. The reactor according to claim 30, wherein each of said branchconnections has valve devices operable for individually controlling therate of supply of the fluidizing gas to the respective containers.

2. The reactor according to claim 1, wherein said gas delivery means ofthe wind box structure comprises nonsifting tuyere units.
 3. A fluidizedbed reactor which comprises a reactor shell of rectangular elongateconfiguration, having a bottom, longitudinal sidewalls, end walls, and aroof, a prefabricated wind box structure built for containing wind boxgas pressure, located in the bottom portion of the reactor shell andsubstantially conforming to the inner contour of said bottom portion,and thus defining a combustion chamber in the complementary upperportion of said shell, said wind box structure having delivery means fordistributing a fluidizing gas into a bed of material to be fluidized;conduit means connected to the wind box structure for supplyingfluidizing air under pressure; feed means for supplying material forcombustion into the combustion chamber, and exit means for thecombustion gases.
 4. The reactor according to claim 3, wherein said windbox structure comprises a plurality of horizontal tubular containers inside-by-side arrangement, an external supply header for the fluidizinggas with branch connections leading from the supply header to theadjacent ends of respective containers.
 5. The reactor according toclaim 3, wherein each of said branch connection have valve devicesoperable for individually controlling the rate of supply of thefluidizing gas to the respective containers.
 6. The reactor according toclaim 3, wherein a plurality of feed devices are provided horizontallyspaced from one another.
 7. The reactor according to claim 3, wherein aplurality of feed devices are provided horizontally spaced from oneanother along one side of the reactor.
 8. The reactor according to claim3, wherein said wind box structure comprises at least one horizontaltubular container coextensive with the longitudinal extent of thereactor.
 9. The reactor according to claim 3, wherein said wind boxstructure comprises a plurality of horizontal containers in aside-by-side arrangement, and communicating with one another.
 10. Thereactor according to claim 3, wherein said reactor shell comprises asequence of tunnel-shaped sections connected endwise to one another soas to constitute a composite reactor system, with a fluidized bedadapted to extend from end to end of the system, each said sectionhaving at least one feed device, a stack for the combustion gases, and aself-contained wind box structure provided with individuallycontrollable air pressure supply devices.
 11. The reactor according toclaim 3, wherein said gas delivery means of the wind box structurecomprises nonsifting tuyere units.
 12. A fluidized bed reactor whichcomprises a reactor shell of rectangular elongate configuration, havinga bottom, longitudinal sidewalls, end walls, and a roof, a prefabricatedwind box structure built for containing wind box gas pressure, locatedin the bottom portion of the reactor shell and substantially conformingto the inner contour of said bottom portion, and thus defining acombustion chamber in the complementary upper portion of said shell,said wind box structure having delivery means for distributing afluidizing gas into a bed of material tO be fluidized; conduit meansconnected to the wind box structure for supplying fluidizing air underpressure; feed means for supplying material for combustion into thecombustion chamber, exit means for the combustion gases, an airpreheater tube system located within the combustion chamber, andcomprising a transverse inlet header located at one end of said chamberand adjacent one end of said wind box structure, a transverse outletheader located at the other end of said wind box structure, a pluralityof tubes arranged side by side and substantially parallel to oneanother, interconnecting said inlet header and said outlet header, acool air supply connection for said inlet header, and a connectionbetween said outlet header and the adjacent end of said wind boxstructure, for passing preheated air into said wind box structure. 13.The reactor according to claim 12, wherein said exit means for thecombustion gases are located adjacent to said inlet header.
 14. Thereactor according to claim 12, wherein a plurality of feed devices areprovided horizontally spaced from one another.
 15. The reactor accordingto claim 12, wherein a plurality of feed devices are providedhorizontally spaced from one another along one side of the reactor. 16.The reactor according to claim 12, wherein said wind box structurecomprises at least one tubular container coextensive with thelongitudinal extent of the reactor.
 17. The reactor according to claim12, wherein said wind box structure comprises a plurality of horizontalducts in side-by-side arrangement, and communicating with one another.18. The reactor according to claim 12, wherein said wind box structurecomprises a plurality of horizontal ducts in side-by-side arrangement,and an external supply header for the fluidizing gas with branchconnections leading from the supply header to the adjacent ends ofrespective ducts.
 19. The reactor according to claim 12, wherein saidwind box structure comprises a plurality of horizontal ducts inside-by-side arrangement, an external supply header for the fluidizinggas with branch connections leading from the supply header to theadjacent ends of respective ducts, and said branch connections areprovided with valve devices operable for individually controlling therate of supply of the fluidizing gas to the respective ducts.
 20. Thereactor according to claim 12, wherein said wind box structure is in theform of a box having a flat top plate and a bottom plate, and isprovided with internal stiffening means connecting the top plate withthe bottom plate.
 21. The reactor according to claim 12, wherein saidstiffening means comprise bolts surrounded by spacer tubes.
 22. Thereactor according to claim 12, wherein said wind box structure comprisesa plurality of ducts of rectangular cross-sectional configurationarranged side by side, and having their top faces extend in a commonplane.
 23. A fluidized bed reactor which comprises a reactor shell ofrectangular elongate configuration, having a bottom, longitudinalsidewalls, end walls, and a roof, said shell being functionally dividedinto a wind box chamber and a combustion chamber above the wind boxchamber, so that a fluidizing gas supplied under pressure to the windbox chamber rising into the reaction chamber will sustain a body ofparticulate material in a fluidized state, conduit means connected tosaid wind box chamber to supply combustion air under pressure, exitmeans for the combustious gases from the combustion chamber, and aplurality of feed devices horizontally spaced from one another along thelength of the reactor.
 24. A fluidized bed reactor which comprises areactor shell, a prefabricated wind box structure built for containingwind box gas pressure, located in the bottom portion of the reactorshell, and defining a treatment chamber in the complementary upperportion of said shell, said wind box structure having delivery means fordistributing a fluidizing gas intO a bed of material to be fluidized,conduit means connected to the wind box structure for supplyingfluidizing gas into the wind box under pressure; feed means forsupplying material to be subjected to fluidization treatment in saidchamber, discharge means for delivering treated material from saidchamber, and exit means for the spent fluidizing gases.
 25. The reactoraccording to claim 24, wherein said gas delivery means of the wind boxstructure comprise nonsifting tuyere units.
 26. A fluidized bed reactorwhich comprises a reactor shell of rectangular elongate configuration,having a bottom, longitudinal sidewalls, end walls, and a roof; aprefabricated wind box structure built for containing wind box gaspressure, located in the bottom portion of the reactor shell, and thusdefining a treatment chamber in the complementary upper portion of saidshell, said wind box structure conforming to said elongateconfiguration, and having delivery means for distributing a fluidizinggas into a bed of material to be fluidized; conduit means connected tothe wind box structure for supplying fluidizing gas into the wind boxunder pressure; feed means located at one end of the reactor, forsupplying material to be subjected to fluidization treatment in saidchamber, discharge means for delivering treated material from saidchamber at the other end of the reactor, and exit means for the spentfluidizing gases.
 27. The reactor according to claim 26, wherein saidgas delivery means of the wind box structure comprise nonsifting tuyereunits.
 28. The reactor according to claim 26, wherein said wind boxstructure comprises at least one horizontal tubular containercoextensive with the longitudinal extent of the reactor.
 29. The reactoraccording to claim 26, wherein said wind box structure comprises aplurality of horizontal containers in side-by-side arrangement, andcommunicating with one another.
 30. The reactor according to claim 26,wherein said wind box structure comprises a plurality of horizontaltubular containers in side-by-side arrangement, an external supplyheader for the fluidizing gas with branch connections leading from thesupply header to the adjacent ends of respective tubular containers. 31.The reactor according to claim 30, wherein each of said branchconnections has valve devices operable for individually controlling therate of supply of the fluidizing gas to the respective containers.